This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A291039 #4 Sep 14 2017 18:15:05
%S A291039 1,3,8,21,54,136,337,825,2000,4809,11484,27264,64401,151455,354808,
%T A291039 828349,1927986,4475080,10361441,23936565,55183904,126983569,
%U A291039 291698040,669004352,1532095329,3503889147,8003207912,18258464741,41608726254,94722900936,215428701233
%N A291039 a(n) = (1/4)*A291038(n).
%H A291039 Clark Kimberling, <a href="/A291039/b291039.txt">Table of n, a(n) for n = 0..1000</a>
%H A291039 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (4, -4, 2, -4, 0, -1)
%F A291039 G.f.: -((-1 + x + x^3)/(-1 + 2 x + x^3)^2).
%F A291039 a(n) = 4*a(n-1) - 4*a(n-2) + 2*a(n-3) - 4*a(n-4) - a(n-6) for n >= 7.
%t A291039 z = 60; s = x/(x - x^3); p = (1 - 2 s)^2;
%t A291039 Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A079978 *)
%t A291039 u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A291038 *)
%t A291039 u/4 (* A291039 *)
%Y A291039 Cf. A079978, A290616, A291038.
%K A291039 nonn,easy
%O A291039 0,2
%A A291039 _Clark Kimberling_, Sep 14 2017